1. Field of the Invention
The present invention relates to an image generation device such as a superimposer or a telop generation device for adding a caption or graphic generated by a computer over a primary picture.
2. Description of the Related Art
Recently an image generation device has been used widely to overlay a graphic image signal with a motion on a background image signal generated by a television camera.
A conventional image generation device will be described hereunder as referring to the attached figures.
Construction of the conventional image generation device is shown in FIG. 1. In the figure the conventional image generation device comprises a graphic data generation unit 1, a graphics processing unit 2, a composing unit 3, an image reproduction unit 4, and a display unit 5.
Operation of the conventional image generation device with the above construction will be described. The graphic data generation unit 1 generates graphic data 11 for a first image frame. The graphic data 11 includes letters, drawings, and location information relating to the drawings. When completing the graphic data 11 for the first image frame, the graphic data generation unit 1 transmits it to the graphics processing unit 2. Receiving the graphic data for the first image frame, the graphic processing unit 2 stores it into an image data memory. After storing the graphic data for the first image frame into the image data memory, the graphic data generation unit 2 generates graphic data for a second image frame. When all the image frames are generated, the graphic data is outputted from the image data memory. Then the composing unit 3 combines graphics 12 with an image signal 13 of a background image recorded by a television camera to generate a composite image signal 14. The display unit 5 reproduces the composite image signal 14 and displays it on a television screen.
Thus, the conventional graphic image generation device generates a graphic image signal by generating graphic data for each image frame. A plurality of graphic data need to be generated for a single image frame to describe a plurality of motions. To generate a graphic image signal with a plurality of motions by the conventional graphic image generation device, the following methods are conceivable.
The same number of the graphic data generation units and the graphics processing units as the graphic data may be operated; and the composing unit may combine all the graphic data with the primary background image signal. Otherwise, the graphic data generation unit generates graphic data first; and the graphics processing unit 2 adds another graphic data thereon. This will be repeated until the number of the graphic data added by the graphics processing unit 2 is consistent with the number of the graphic data. Then, all the graphic data are combined with the primary background image by the composing unit.
Each of the above conceivable methods to be employed by the conventional image generation device has its own drawback. That is, having the same number of the graphic data generation units and the graphics processing units as the graphic data increases the size of the image generation device; while adding another graphic data on the previously generated graphic data in a repeated manner costs much labor.